#include<stdio.h>
#include<string.h>
#include<math.h>
struct S
{
    double x1, y1, x2, y2, x3, y3;
}sjx;
int main()
{
      double p=0,s,a,b,c;
      scanf("%lf %lf %lf %lf %lf %lf", &sjx.x1, &sjx.y1, &sjx.x2, &sjx.y2, &sjx.x3, &sjx.y3);
      p=p+sqrt(pow(sjx.x1-sjx.x2, 2) + pow(sjx.y1-sjx.y2, 2));
      a = p;
      p=p+sqrt(pow(sjx.x1-sjx.x3, 2) + pow(sjx.y1-sjx.y3, 2));
      b = p - a;
      p=p+sqrt(pow(sjx.x2-sjx.x3, 2) + pow(sjx.y2-sjx.y3, 2));
      c = p - a - b;
      p = p / 2.0;
      s = sqrt(p * (p - a) * (p - b) * (p - c));
      printf("%.2lf\n",s);
      return 0 ;
}